The present invention relates to a channel tuner mechanism for a high power klystron. The high power klystron is comprised of an electron gun for emitting and forming an electron beam, interaction structure for interacting a radio frequency signal with the electron beam, a collector for collecting electrons, and a magnetic focusing for focusing the electron beam. Among them, the interaction structure is comprised of a main part of a cavity, a plunger, and a channel tuner mechanism connecting and supporting the plunger. When varying a frequency of the radio frequency signal to be amplified, it is necessary to adjust adequately resonant frequencies of a plurality of cavities while monitoring repeatedly frequency characteristics of the high power klystron. Therefore, the conventional klystron is inconvenient with respect to maintenance and operation as compared to traveling wave tube which also amplifies an electromagnetic wave.
In order to remove this operational inconvenience, there has been proposed a particular type of the high power klystron provided with a channel tuner mechanism having a preset function effective to easily determine a given frequency band width for preset particular frequencies by a channel switching operation without adjusting the resonant frequencies. This type of the conventional high power klystron provided with such preset function has a construction as shown in FIG. 1.
Namely, in the high power klystron, the interaction structure is comprised of a cavity 1, a plunger 2 for changing a volume of the cavity 1 to vary a resonant frequency, and a piece of bellows 3 connected to both of the plunger 2 and the cavity 1 to expand or contract in order to effect advancing and retracting movement of the plunger 2 while maintaining the vacuum state of the high power klystron. Further, a channel tuner mechanism 4 is comprised of a plunger support mechanism 5 connected to the plunger 2 for moving in a given direction along an axis of the plunger 2, and a preset unit 7 fixed to the interaction structure through a supporting rod 6. The channel tuner mechanism 4 is connected to the plunger 2 so as to vary a resonant frequency of the cavity 1, and this mechanism 4 is comprised of the plunger support mechanism 5 for applying normally to the plunger 2 a force in a reverse direction away from a vacuum tube side of the high power klystron by means of a restoring force of a spring 8, the preset unit 7 including means for displacing in a parallel manner a preset plate 10 which is provided with a plurality of frequency setting screws 9, by rotating a channel select shaft 19 and pinion 11, and a drive mechanism 13 for effecting a coupling and decoupling between the frequency setting screws 9 and tuner shafts 13. FIG. 2 shows a detailed construction of the preset plate 10, pinion 11 and frequency setting screws 9.
In this mechanism, preset operation is carried out as follows in order to preset a predetermined frequency band width in a particular tuning channel of the high power klystron be means of each set of the frequency setting screws 9 disposed along drift tube tips of the cavity. At first in the FIG. 1 state, the adjustment is carried out by the frequency setting screws 9 so as to set a frequency band width in a given channel. Next, a movable plate 17 is displaced to come in contact with an unlock plate 18 by rotating a lock-unlock shaft 16 which is fixed to a fixing plate 15 through a set of bearings 14. At this moment, the tuner shaft 12 connected to the plunger 2 is decoupled from the frequency setting screw 9. In this state, a channel shaft 19 is rotated such that another frequency setting screw 9 is positioned in alignment with a center axis of the tuner shaft 12. In this position, the movable plate 17 is again displaced through the lock-unlock shaft 16 to come in contact with a lock plate 20. In this state, an advancing degree of the frequency setting screw 9 is adjusted to set a predetermined frequency band width characteristic in another channel than the first tuned channel. Such adjustment is repeatedly carried out so as to provisionally set a multiple of tuning channels in the high power klystron.
However, in the above described conventional channel tuner mechanism, it is necessary to provisionally memorize setting data in a memory of an apparatus in which the klystron is mounted as to which channel is tuned in the klystron. The reason is that it is necessary to recognize which channel is selected for tuning of the klystron and to recognize which channel is next selected for tuning of the klystron when channel switching is carried out in the channel tuner mechanism. However, this memorizing method has various drawbacks because a costly memory device is needed, and a memory device of such a complicated construction may cause a failure.